Through the years numerous refining methods for lubricating oils have been used. Many of these include low-pressure fractionation, solvent extraction, solvent dewaxing, acid treating, and clay treating. Such lubricating-oil treatments are discussed in Kirk-Othmer "Encyclopedia of Chemical Technology," volume 10, The Interscience Encyclopedia, Inc., New York, pp. 54-61 (1966).
More recently, hydrotreating has been used as a means for improving the quality of both raw lubricating-oil stocks and waxes. Such hydrogenation processes have been used generally to improve the color and stability of the oil or wax.
Catalysts employed in the hydrogenation of liquid hydrocarbons become contaminated over a period of time with combustible carbonaceous impurities, thereby resulting in a serious decrease in the activity of the catalyst. The deposition of carbonaceous material on the catalyst is particularly pronounced in the case of catalysts used in hydrotreating of heavy hydrocarbon oils. When the activity of the catalyst has declined to an undesirably low level, the activity of the catalyst may be restored to a considerable degree by burning the carbonaceous contaminants thereon. Procedures for regenerating deactivated hydrogenation catalyst have generally involved contacting the catalyst particles with steam and molecular oxygen at elevated temperatures.
Unfortunately, high temperature steam-oxygen regeneration operations sometimes result in serious side effects, such as sintering of the carrier, e.g., alumina, and sublimation or migration of the metallic components of the catalyst. Furthermore, such catalyst regeneration often requires an unduly long period of time to restore the activity of the catalyst to the desired level. Thus, high temperature steam-oxygen regeneration operations have a number of serious drawbacks. The current invention overcomes these disadvantages.